The performance of tillage implements for soil loosening is different. Tillage tools used high draft force. The selection of suitable tillage equipment can save energy and affect the final seed bed conditions. Power harrows or vertical rotary plows do not bring soils to the surface, causing conserving soil moisture content and require less draft force to loose soil because it using PTO. Since the aim of tillage tool design is to create a mechanical system with less energy spent, the modal analysis and measuring of torsional torque for vertical rotary plow blades in the different soil physical conditions was investigated. The torque applied to the drive shaft of the tillage blades was measured by installing the four-shear strain gauge as a whetstone bridge circuit, with amplifiers and a data accusation system, model Vista 24-bit resolution and 10 Hz. Factorial experiments in a completely randomized design with the factor (a) type of blade in three levels (vertical rotary plow blade, rotary single bent-leg blade and cutting edge curved (RC)) (b) soil compaction in two levels of 1.2 and 1.9 g/cm 3 , and (c) soil moisture in two levels of 0.5 PL and 0.9 PL at three replications were compared by measuring the torque and length of soil rupture. Dimensions of the blade was based on the dimensions of the vertical rotary plow blade of Gaspardo Italian Co., tge depth was based on the depth of working of vertical rotary plow blade, different levels of moisture and soil compaction based on soil dry weight in the preliminary experiments. The effect of each treatment and their interaction with Statistix 8.0 statistical software and the modal analysis of the blades by SolidWorks finite element software were evaluated. The results showed the highest and lowest torque value at a rate of 1033.3 N-m in 0.9 PL and 390.8 N-M in 0.5 PL for rotary single bentleg and RC blade, respectively. The highest and lowest rupture distance at the rate of 13.73 cm for 0.9 PL and 10.8 cm for 0.5 PL was obtained in rotary single bentleg and RC blade, respectively. Since the soil conditions are not constant oscillating frequency was measured. Vibratory stresses maks plastic deformation, so the determining the natural frequencies of the blade to avoid excessive stress resonance was measured. Three-dimensional modeling of the vertical rotary plow blade was done by CAE engineering CATIA and ABAQUS and SolidWorks Simulation (COSMOS) for natural frequency and mode shape analysis vibration of the blades was used. Modal analysis (vibration analysis) to determine the intrinsic dynamic in terms of natural frequencies, damping coefficients, modes shape, and applying them to create a mathematical model of the dynamic behavior was used. Modal analysis of the vertical rotary plow blade showed that the first six frequencies were close to zero (rigid motion in the longitudinal direction, rigid motion in the transverse direction, rigid motion in the vertical direction, the rotational rigid motion in the longitudinal direction, rotational rigid motion the transverse direction and rotational rigid motion in the vertical direction), indicating the rigid motion. The seventh mode natural frequency of the blades (bending at the blade hitching to the machine) was determined at the rate of 580.35 Hz, 926.64 Hz and 444.16 Hz resonant frequency in the vertical rotary plow, rotary single bent-leg, and RC blade, respectively. Since the frequency of the vertical rotary plow blades is less (about 60 Hz), risk of resonance phenomenon of the blades is very low. In other words, the frequency of the applied force should not be equal to the blade natural frequency in the seventh mode, because the plastic deformation and damage occurred. Maximum displacement of the blades, were at the rate of 2.052 mm, 2.45 mm and 2.92 mm in the eighth mode (bending in blades hitting area with soil), ninth mode (bending in the YZ plane and tilting) and tenth mode (bending and torsion in the YZ plane) related to the vertical rotary plow, RC, and rotary single bentleg blade, respectively. Among these blades, rotary single bentleg and RC blade had the maximum and minimum torque value and rupture distance, respectively. Vertical rotary plow is desirable in terms of torque and rupture distance can be better. The highest and lowest viscosity and yield stress in the moisture content of 0.5 PL and 1.9 g/cm 3 bulk density and 0.9 PL and 1.2 g/cm 3 bulk density was obtained, respectively. Viscosity and yield stress decreased with increasing moisture content and decreasing bulk density. Keywords : cyclotiller, rotary harrow, torsional torque, modal analysis, soil cutting